1. Field of the Invention
The present invention relates to a rotary or angle encoder including a carrier member, and a measurement tape securable on the bearing surface of the carrier member by being clamped thereto, with the length of the measurement tape and the circumference of the bearing surface being so conformed to each other that the measurement tape lays on the bearing surface backlash-free in its mounted condition after having been snap-fitted on the bearing-surface.
2. Description of the Prior Art
An angle encoder of the type described above is described in German Patent DE 43 31 668 C2. A measurement tape is secured on the concave, curved inner wall of a carrier member. The length of the measurement tape and the circumference of the inner wall are so conformed to each other that the measurement tape lays backlash-free on the inner wall after being snap-lifted thereon.
However, in practice, it is relatively difficult to realize this conformity. If the measurement tape is too short, it does not lay over the entire length on the inner wall. If the measurement tape is too long, it lays, after being snap-fitted, over its entire length backlash-free on the inner wall. However, the press-on force, with which the measurement tape lays on the inner wall after being snap-fitted, is too large, so that, because of rope friction, the measurement tape cannot freely expand, and a non-uniform pressure profile is observed over the entire length of the measurement tape. The pressure profile causes a partial length change of the measurement tape and, thus, leads to measurement errors.
Accordingly, an object of the invention is to provide an angle encoder in which the measurement tape is secured by being snap-fitted and the circumference of the inner wall and the length of the measurement tape can be easily conform to each other.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing, on the bearing surface of the inner wall, two, spaced from each other, stop surfaces, which are engaged, in the mounted condition of the measurement tape, by opposite ends of the tape, and by providing an adjustment element for adjusting a position of at least one stop surface so that a distance between the two stop surfaces and thereby a length of the bearing surface circumference correspond to a length of the measurement tape. Thereby the measurement tape lays on the bearing surface circumference, in its mounted conditions backlash-free after having been snap-fitted.
These measurers permits to conform the length of the circumference of the inner wall, on which the measurement tape lays, to the length of the measurement tape, so that the press-on force, which is applied by the measurement tape to the inner wall, can be easily adjusted and optimized.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.